Background: Afebrile Plasmodium falciparum infections usually
remain undetected and untreated in the community and could
potentially contribute to sustaining local malaria transmission
in areas aiming for malaria elimination. Methods: Thirty-two men
with afebrile P. falciparum infections detected with rapid
diagnostic test (RDTs) were followed for 28 days. Kaplan-Meier
estimates were computed to estimate probability of parasite
positivity and of reducing parasitaemia by half of its initial
level by day 28. Trends of parasite densities quantified by
microscopy and qPCR were assessed using Poisson regression
models, and the microscopy to qPCR positivity ratio was
calculated at each time point. Three survival distributions
(Gompertz, Weibull, and gamma) were used to evaluate their
strength of fit to the data and to predict the median lifetime
of infection. Results: The cumulative probability of parasite
qPCR positivity by day 28 was 81% (95% CI 60.2-91.6). Geometric
mean parasitemia at recruitment was 516.1 parasites/muL and fell
to <100 parasites/muL by day 3, reaching 56.7 parasites/muL
on day 28 (p-value<0.001). The ratio of P. falciparum
positive samples by microscopy to qPCR decreased from 0.9 to
0.52 from recruitment to day 28. The best model fit to the data
was obtained assuming a Gompertz distribution. Conclusions:
Afebrile P.falciparum infections detectable by RDT in
semi-immune adults fall and stabilize at low-density levels
during the first four days since detection, suggesting a rapid
decline of potential transmissibility in this hidden parasite
reservoir.